1. Field of the Invention
The present invention relates to a measuring apparatus for measuring the properties of a probe card (e.g., displacement attributable to the deflection of the probe card under measurement) used in a probe unit, the probe unit having the measuring apparatus, and a probing method.
2. Description of the Related Art
In an inspection process for a semiconductor apparatus, for example, a probe unit is widely used to check a semiconductor wafer (hereinafter referred to simply as a xe2x80x9cwaferxe2x80x9d). Usually, the probe unit comprises a loader chamber and a prober chamber. The loader chamber comprises a carrier stage portion, a wafer transportation mechanism, and a pre-alignment mechanism (hereinafter referred to as a xe2x80x9csub-chuckxe2x80x9d). The carrier stage portion carries thereon carriers that store a plurality (e.g., 25) of wafers. The wafer transportation mechanism transports the wafers one after another from the carrier stage portion. The sub-chuck pre-aligns the wafers that are transported by means of the wafer transportation mechanism. The prober chamber comprises a stage (hereinafter referred to as a xe2x80x9cmain chuckxe2x80x9d), moving mechanism, probe card, alignment mechanism, and test head. The main chuck carries the wafer thereon. The moving mechanism moves the stage in the X-, Y-, Z-, and xcex8-directions. The probe card is located over the main chuck. The alignment mechanism, in conjunction with the moving mechanism for the main chuck, aligns the wafer with respect to the position of the probe card. The test head is located between the probe card and a tester.
In measurement, the main chuck carrying thereon a wafer that is aligned with the probe card is raised. Probes of the probe card are brought into contact with electrodes of a semiconductor device (hereinafter referred to as a xe2x80x9cdevicexe2x80x9d) on the wafer under an optimum probe pressure. Specified electrical properties of the device are measured in a manner such that a signal for measurement from the tester is applied to the device and received through the test head and the probes. Then, the main chuck that carries the wafer thereon is indexed, and the properties of the device are measured in succession by repeating the aforesaid steps of procedure. Electrical contact between the electrodes of the device and the probes can be secured by overdriving the main chuck for a given value in bringing the electrodes of the device and the probes into contact with one another.
When the main chuck is in an overdriven state, however, the probe card receives a force of pressure from the main chuck through its probes. In consequence, the probe card is displaced in the vertical direction (Z-direction). This displacement varies depending on the static stiffness of the probe card and the main chuck.
Conventionally, a measuring apparatus that is provided with a laser displacement gage measures this static stiffness. This measuring apparatus comprises a plate equal to the probe card in diameter and having mechanical properties similar to those of the probe card, a cylinder mounted on the plate, and the laser displacement gage. In measuring the static stiffness, the plate of the measuring apparatus is attached to an attachment region of the probe card. In this state, the same load for the overdriving operation is applied to the main chuck through the cylinder on the plate. The laser displacement gage measures the displacement of the main chuck in the Z-direction.
In a measuring method based on the conventional measuring apparatus, however, the plate is attached to the attachment region of the probe card, so that the displacement of the probe card in the Z-direction is ignored. More specifically, in the conventional measuring apparatus, the main chuck is pressed by means of the cylinder that is attached to the plate. In this pressed state, the laser displacement gage that is attached to the plate measures the Z-direction displacement between the plate and the main chuck. Therefore, the plate itself is bent by the force of pressure from the cylinder. The laser displacement gage can measure the comparative displacement (relative displacement) between the main chuck and the probe card that involves the deflection of the probe card. However, the Z-direction displacement (absolute displacement) of the plate that is attributable to the deflection cannot be measured.
The deflection of the plate as the alternative of the probe card is different from that of the probe card. In consequence, the deflection of the probe card under actual inspection cannot be measured accurately.
Thus, the absolute displacement of the probe card cannot be measured, so that the relation between the overdrive value of the main chuck and load cannot be obtained accurately. It is hard to set the overdrive value of the main chuck appropriately.
With the development of wafers having larger diameters and ultrahigh-integration devices, development of larger multi-pin probe cards has recently been promoted. In consequence, the load from the probe card that acts on the main chuck becomes heavier, so that the displacement of the probe card increases. The substantial displacement of the probe card has an influence upon the reliability of the measurement.
Based on these circumstances, the absolute displacement of the probe card can be measured according to the present invention. According to embodiments of the present invention, the relation between the overdrive value of the stage and the load can be obtained accurately, and the appropriate overdrive value can be set.
According to the first aspect of the present invention, there is provided a measuring apparatus for measuring the properties of a probe card, comprising: a stage; a holding mechanism located over the stage (the holding mechanism holding a probe card having probes or a probe card having no probes); a lift mechanism which causes the stage to ascend and descend toward the probe card; a load sensor which detects the load the stage receives from the probe card when the lift mechanism rises toward and brings the stage into contact with the probe card; and a displacement sensor which detects the absolute displacement of the probe card, which has been caused by the load.
It is desirable to arrange the contact block on the stage in the measuring apparatus.
It is also desirable that the load sensor be provided between the stage and the contact block in the measuring apparatus.
Preferably, at least one of the load sensor and the displacement sensor is removably located in the apparatus.
Preferably, the displacement sensor of the measuring apparatus measures at least one of the displacement of the probe card and the stage.
Preferably, the displacement sensor of the measuring apparatus measures the displacement of the contact block.
Preferably, the displacement sensor of the measuring apparatus detects the position of the contact block when the probe card and the contact block contact each other and when the stage further moves up and receives a prescribed load from the probe card.
Preferably, the displacement sensor of the measuring apparatus is an eddy-current displacement sensor.
Preferably, the load sensor of the measuring apparatus is placed on the stage.
Preferably, the measuring apparatus has a positioning plate for positioning the load sensor on the center part of the stage.
Preferably, the displacement sensor of the measuring apparatus detects at least one of the position of the probe card and the position of the stage when the probe card and the stage contact each other and when the stage further moves and receives a prescribed load from the probe card.
Preferably, the measuring apparatus further comprises a memory which stores the measured characteristic values of the probe card.
According to another aspect of the invention, there is provided a measuring apparatus for inspecting the electrical properties of an to-be-inspected object. The apparatus comprises: a stage which holds the to-be-inspected object, a holding mechanism which is provided above the stage the holding mechanism holds one of a probe card having a plurality of probes and a probe card having no probes; a lift mechanism which moves up the stage toward the probe card and moving down the stage from the probe card; a load sensor which is removable and detects a load which the stage receives from the probe card when the lift mechanism moves up the stage, and a displacement sensor which is removable and detects an absolute displacement which the probe card undergoes upon receiving the load.
Preferably, the probe apparatus comprise a contact block which is removably provided on the stage.
Preferably, the load sensor is provided between the stage and the contact block.
Preferably, the probe apparatus comprise a storage unit which stores data which represents a relation between an over-drive distance and a probe pressure of the probe, the over-drive distance and the probe pressure being based on the absolute displacements measured at different temperature.
Preferably, the measuring apparatus further comprises a contact block removably located on the stage.
Preferably, the displacement sensor of the measuring apparatus measures the displacement of at least one of the probe card and the stage.
Preferably, the displacement sensor of the measuring apparatus measures the displacement of the contact block.
Preferably, the displacement sensor of the measuring apparatus is an eddy-current displacement sensor.
Preferably, the load sensor of the measuring apparatus is removably placed on the stage.
Preferably, the measuring apparatus further comprises a memory which stores the measured characteristic values of the probe card.
According to the third aspect of the present invention, there is provided a method of measuring the properties of a probe card, comprising: (a) holding one of a probe card having probes and a probe card having no probes by means of a holding mechanism; (b) raising and bringing a stage into contact with the probe card; (c) overdriving the stage; (d) detecting the load the stage receives from the probe card by the overdriving; (e) detecting the absolute displacement of the probe card by the overdriving ((d) and (e) being executable in the order of (d) and (e) or in the order of (e) and (d)).
Preferably, in this method, the detection of the load of (d) and the detection of the displacement of (e) are carried out at a plurality of temperatures.
Preferably, this method further comprises (f) storing in a memory at least one of the detected load and displacement.
Preferably, in this method, the detection of the load of (d) and the displacement of (e) are carried out by using the probe card having probes, the detection of the load of (d) and the detection of the displacement of (e) are carried out by using the probe card having no probes, and a given overdrive value is calculated in accordance with the two detected displacements.